Bidirectional Spillover of SARS-CoV-2 Between Humans, White-Tailed Deer

In a new study appearing in Nature Communications, researchers from the University of Missouri and elsewhere find SARS-CoV-2 among free-ranging white-tailed deer populations in the US. Previous studies had shown that SARS-CoV-2 virus can readily infect white-tailed deer and lead to high loads of viral shedding, and the researchers noted that it seems to have now become enzootic. For their analysis, the researchers collected 8,830 respiratory samples from free-ranging white-tailed deer from across Washington, DC, and 26 US states between November 2021 and April 2022. The sequencing data revealed that the virus belonged to multiple lineages — Alpha, Gamma, Delta, and Omicron — but many of these SARS-CoV-2 lineages were present in white-tailed deer months after the decline of those lineages in the human population, the researchers note. Evolutionary analysis also showed that the virus in white-tailed deer came from at least 109 independent spillover events from humans, and that there were 39 subsequent local deer-to-deer transmission cases and three cases of potential spillover from white-tailed deer back to humans, the authors say. "Overall, these potential instances highlight the possibility for bi-directional transmission of SARS-CoV-2 at the human-white-tailed deer interface," the researchers write.